JPH0146570B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrical resistance alloy consisting of palladium (Pd) and iron (Fe) as main components, containing a small amount of impurities, and stable at ultra-high temperatures, and a method for producing the same.
The object of the present invention is to obtain a material that exhibits small changes in electrical resistance over a wide temperature range of 1340°C or less, and that can be easily processed by forging, rolling, wire drawing, or wire winding at room temperature. In recent years, various types of measurements under extremely harsh conditions have become popular in industries such as the steel industry, chemical industry, nuclear industry, and space-related industry. For example, in a continuous casting process that enables integrated production of high-yield, high-quality steel, it is necessary to constantly control the level of the molten metal in the tundish or mold in order to maintain it at a desired level. Conventionally, methods using radiation such as gamma rays and The use of a displacement meter (hereinafter simply referred to as a displacement meter) has become possible. Incidentally, since the performance of a displacement meter is determined by the sensor coil material, its electrical characteristics, usage environment, stability, etc. are extremely important. For example, the temperature of the molten metal in continuous casting reaches over 1500℃, so the temperature of the sensor coil material located directly above it is 1000℃.
It must not only withstand high and low temperatures, but most importantly, it must have excellent properties and be stable over a long period of time. As a conventional high-temperature sensor coil material, there is a well-known alloy (Japanese Patent Laid-Open No. 122839/1983) invented by the present inventors and consisting mainly of palladium and silver. This alloy not only has good corrosion resistance, oxidation resistance, and workability at high temperatures, but also has good resistance to temperatures between -50 and 600℃, as can be seen from the characteristic curve of the comparative alloy shown in Figure 1.
The temperature coefficient of electrical resistance is extremely small at +20ppm/℃ or less over a wide temperature range, but at even higher temperatures of 600 to 1000℃
Since the value is as large as 133 ppm/℃, high drift occurs when used at extremely high temperatures such as in the continuous casting process mentioned above, and the accuracy of the displacement meter due to temperature changes rapidly decreases, making accurate measurement impossible. Can not. Therefore, there has been a strong demand from various industries for the development of novel ultra-high temperature sensor coil materials that have high accuracy and good stability at higher temperatures of 600°C or higher. In response to this, the present inventors conducted further detailed research and found that palladium contained 72.0 to 86.5%.
The melting point (1340℃) is higher than the ordered-disorder transformation temperature (570℃) and the balance iron and a small amount of impurities.
It is an electrical resistance alloy for ultra-high temperature sensor coils that has extremely small changes in electrical resistance over a wide range of temperatures below ℃), has excellent electrical resistance stability at high temperatures, and has good workability. I found out. That is, the present invention has a weight ratio of palladium of 72.0 to
It is composed of 86.5% iron and 28.0 to 13.5% iron, and contains a small amount of impurities, and the temperature coefficient of electrical resistance is ± within a wide temperature range from the regular-irregular transformation temperature to 1340°C.
An electrical resistance alloy for ultra-high temperature sensor coils having a resistance of 50 ppm/℃ or less and a method for manufacturing the same, which is further annealed at a temperature above the regular-irregular transformation temperature and below the melting point to achieve excellent stability. The present invention provides a method for producing an alloy that exhibits the electrical properties of the present invention. In addition, the alloy of the present invention is not only used in ultra-high temperature sensor coils, but also in 570
Since the alloy of the present invention is suitable as an electrical resistor element for precision measuring instruments, including various sensors that can exhibit the characteristics of the present alloy at ultra-high temperatures of ℃ or higher, it is also possible to apply it as a composite of these devices. Next, the method for manufacturing the alloy of the present invention will be explained in detail. To make the alloy of the present invention, palladium 72.0 ~
Appropriate amounts of 86.5% iron and 28.0 to 13.5% iron are melted in a non-oxidizing atmosphere or in vacuum using a suitable melting furnace and thoroughly stirred to obtain a compositionally uniform molten alloy. Next, the molten alloy is poured into an iron mold of an appropriate shape and size to obtain a sound ingot, which is then subjected to casting and other various processing at room temperature to produce an object of an appropriate shape, such as a rod or plate. Further, this is subjected to cold working by methods such as swaging, wire drawing, rolling, or crushing to obtain a desired shape, such as a thin wire or a thin plate. Finally, when using the thin wire or thin plate as an electrical resistance alloy element, in order to stabilize the cold-worked product, it is placed in a non-oxidizing atmosphere or in vacuum at a temperature above the ordered-disorder transformation temperature and below the melting point. at least the measurement temperature or higher, for example, the upper limit of the product's operating temperature is 1000
℃, it is necessary to heat it to 1050℃ or higher, hold it for 5 minutes or more and 50 hours or less, and then cool it at 5 to 300℃/h to perform sufficient annealing. These manufacturing processes yield excellent products. The most important thing in the above manufacturing process is that since the alloy of the present invention has a strong affinity for air or oxygen, as is clear from Figure 2, contact with air causes a significant deterioration in electrical resistance. In addition, it is important to be careful because it may cause an adverse effect on cold workability in the manufacturing process. In other words, it is natural that contact with air or oxygen must be avoided as much as possible during the melting process, but in addition to this, the above points must also be taken into consideration when applying various heat treatments in the manufacturing process after melting and when applying it as a sensor device. Must pay attention. Furthermore, as mentioned above, the alloy of the present invention is not only oxidized, but also changes into an ordered state (γ ₁ phase and γ ₂ phase) alloy, which has hard and brittle properties like an intermetallic compound, depending on the heat treatment method. There are some things that can damage your sexuality. Therefore, in order to further improve processability, it is necessary to use an appropriate method during processing from a temperature above the regular-irregular transformation temperature to below the melting point, such as by spraying non-oxidizing gas at high speed, or by rapidly cooling in oil. Alternatively, it is necessary to create an alloy in a disordered state (γ single phase) by rapidly cooling it by placing it in ice salt water while vacuum-sealing it in a quartz tube, and to give it good workability at room temperature. be. According to this method, the thin wire or thin plate that has been rapidly cooled before processing becomes very soft and can be easily wound into a coil or spiral shape. A manufacturing method that provides good workability as described above is also one of the features of the present invention. Next, as a method for insulating the above-mentioned alloy, the following three types of processes can be considered. (A) The alloy of the present invention is processed by casting, forging, rolling, wire drawing, etc. into a desired shape such as a wire or plate, and then embedded as is in a heat-resistant insulator such as high-purity ceramic paste. Alternatively, it can be fixed by directly attaching it to a heat-resistant insulator with alumina adhesive, wrapping it around a cylindrical ceramic, or sandwiching it between two insulating plates. (B) A method for increasing the space factor of the sensor coil is to add heat-resistant silica, alumina, magnesia, fluoride, or After applying or coating an inorganic insulating film such as boride or titanide by an appropriate method such as electrodeposition, vapor deposition, plating or sputtering, the wire is formed into a desired shape. (C) After forming a heat-resistant insulating film on the surface of the molded body of the alloy of the present invention by an appropriate method such as electrodeposition, vapor deposition, plating, or sputtering,
Perform etching punching or trimming into any shape. The product completed through the above process can be used as is, but if necessary, it can be annealed again using the method described above to stabilize the alloy material, so that it has the same characteristics as the electrical resistance alloy itself. It is possible to manufacture ultra-high temperature sensor coils or electrical resistor elements that exhibit excellent performance. Next, embodiments of the present invention will be described. Example 1 Alloy number Alloy FP-18 (composition Pd=86.5%,
Production of Fe=13.5%) Palladium with a purity of 99.9% or higher and iron with a purity of 99.9% or higher were used as raw materials. To make a sample, put raw materials with a total weight of 100g into a high-purity alumina crucible,
To prevent oxidation, the surface was blown with high purity argon gas and melted in a high frequency induction electric furnace, stirred well to make a homogeneous molten alloy, and then the inner diameter was 7 mm.
It was cast into an iron mold with a height of 180mm. After removing surface defects, the ingot was cold-worked to a diameter of 5 mm by swaging. Next, after homogenization treatment was performed at 1150°C in vacuum, water quenching was performed at 1000°C, which is higher than the regular-irregular transformation temperature (570°C). Subsequently, water quenching was repeated several times during the process, followed by swaging and cold wire drawing to form a thin wire with a diameter of 0.5 mm, and a wire with a length of about 10 cm was cut out to be used as a sample for measuring electrical resistance. Electrical resistance was measured in a temperature range of room temperature to 1300°C in vacuum. As shown in Figure 1, the change in electrical resistance during processing (broken line) is due to the instability of the structure. →a' or b→b', the original path is not followed and hysteresis occurs. However, the regular-disorder transformation temperature (T _pd = 570
In the annealed state (solid line) from temperatures above ℃),
Other than a small hysteresis loop occurring near T _pd , it follows the same path even if the temperature is repeatedly increased. and
The change in electrical resistance at temperatures above T _pd is T _pd
It can be seen that this is extremely small compared to the case at the following temperatures. The characteristics corresponding to the heat treatment conditions of the samples are shown in Table 1.

[Table] Items 1, 2, and 3 in the table are
The average temperature coefficient of electrical resistance in the temperature ranges 800-900°C, 900-1000°C and 800-1000°C is shown. The smaller the difference between the values of the first to third terms, the smaller the quadratic coefficient becomes and the electrical resistance changes linearly. Then, the temperature is raised to 1300℃ and then cooled.
No change in electrical resistance was observed even when kept at 1000°C for 50 days and 1100°C for 20 days. Example 2 Alloy number Alloy FP-24 (composition Pd=80.2%, Fe
= 19.8%) Palladium and iron of the same purity as in Example 1 were used as raw materials. The sample was manufactured by placing a total weight of 10 g into a high-purity alumina crucible (SSA-H, #2), melting it in a Tamman furnace while blowing high-purity argon gas onto the metal surface to prevent oxidation, and stirring well. A homogeneous molten alloy was obtained. Next, set this to the inner diameter
The sample was sucked up into a 2.6 to 2.7 mm quartz tube, and for homogenization treatment, the sample was inserted into a quartz tube sealed at one end with an inner diameter slightly larger than the diameter of the sample, held at a temperature of 1000°C for 10 minutes, and then water quenched. Subsequently, the wire was made into a fine wire with a diameter of 0.5 mm by swaging and cold wire drawing. A sample of approximately 10 cm in length was cut from this. The heat treatment conditions of the sample and the corresponding characteristics are shown in Table 2 and FIG. 1, and show similar trends to those in Example 1.

[Table] Example 3 Alloy number Alloy FP-19 (composition Pd=73%, Fe=
27%) Production The raw materials and production method are the same as in Example 2.
The heat treatment conditions of the samples and the corresponding characteristics are shown in Table 3 and Figure 1.
shows a similar trend.

[Table] Figure 3 shows that experiments similar to those in Examples 1 to 3 were conducted over the entire palladium-iron binary system.
Temperature range (800~900℃), Temperature range (900~
1000°C) and the average temperature coefficient of electrical resistance in the temperature range (800 to 1000°C) C _f =ΔR/R·ΔT and the specific electrical resistance ρ ₉₀₀ at 900°C are shown with respect to the amount of Pd. From the figure, the characteristics when C _f is ±100 ppm/℃ or less are palladium 59.0 to 88.0% (A to D).
Also, the characteristics with C _f of ±50ppm/℃ or less are palladium.
It can be seen that the composition is 72.0 to 86.5% (B to C). temperature range, and
The larger the difference between the values of C _f (), C _f (), and C _f (), the larger the quadratic coefficient, and conversely, the smaller the difference between them, the smaller the quadratic coefficient. For example, the point A where C _f (), C _f () and C _f () intersect
Since the quadratic coefficient is 0, the electrical resistance changes linearly between 800 and 1000°C. Figure 4 is the iron-palladium system phase diagram, and the shaded area is palladium 72.0-86.5% and iron 28-13.5%.
It has been shown that the alloy of the present invention consisting of has a temperature coefficient of electrical resistance C _f of ±50 ppm/°C or less. It can be seen that all of the above properties can be obtained in a wide temperature range between the regular-disorder transformation temperature and the melting point, from 570°C to 1335°C. In Figure 1, in the case of alloy number FP-24, there is a small portion of the electrical resistance change near about 400°C on the curve, but it changes discontinuously at the ordered-irregular transformation temperature. Because it does not have the characteristic that the change in electrical resistance is small over a wide range of temperatures,
Not shown in Figure 4. As described above in Examples 1 to 3, the alloy of the present invention exhibits a small change in electrical resistance with respect to temperature in all cases. In particular, alloy number FP-18 of Example 1 has a large specific electrical resistance _ρ900 of 100 μΩ-cm, but it
The change in electrical resistance is extremely small and reproducible over a wide temperature range, indicating that the product has good stability. In this way, there is no known example of a single material having a small temperature coefficient of less than ±50 ppm/°C over a wide temperature range of 570°C to 1335°C, which is a requirement for ultra-high temperature sensor coil alloys. It can be said that the characteristics are fully satisfied. Next, palladium is added to the composition of the alloy of the present invention.
The reason for limiting the range to 72.0 to 86.5% is explained in each example and the first
As is clear from Figures 3 and 4,
The temperature coefficient of electrical resistance in the temperature range of 570°C to 1340°C exhibits a characteristic of ±50 ppm/°C or less, but if the composition is outside this range, it becomes larger than the above value, so the change in electrical resistance over a wide range of temperatures is This is because it is inappropriate as a small alloy. Furthermore, in the method for producing the alloy of the present invention, the reason why the quenching treatment before annealing is limited to a temperature range from the regular-irregular transformation temperature (570°C) to the melting point (1340°C) is explained in each example and in Figure 1. , as is clear from Figures 3 and 4, rapid cooling from the above temperature range induces a single γ phase (irregular state), which can provide better workability at room temperature. If the temperature is below the ordered-irregular transformation temperature, the alloy becomes extremely brittle and hard, which not only makes processing difficult at room temperature, but also poses a problem in wire-wound forming operations, making it unsuitable as a method for producing the alloy of the present invention. It is. Furthermore, a manufacturing process in which rapid cooling treatment and annealing treatment are contradictory is not suitable as a manufacturing method for the alloy of the present invention because the annealing treatment makes the alloy extremely brittle and hard, making subsequent winding forming processing difficult. . In short, the alloy of the present invention has an extremely small change in electrical resistance of ±100 ppm/°C or less over a wide temperature range from the ordered-disorder transformation temperature (570°C) to the melting point (1340°C), and even at extremely high temperatures such as 1100°C. It is extremely stable for a long period of time, and has many features such as its workability being further improved by rapid cooling from a temperature above the regular-irregular transformation temperature (570℃) and below the melting point (1340℃). Therefore, it is suitable not only for ultra-high temperature sensor coils but also as electrical resistor elements for precision measuring instruments, including reference resistors used in a wide temperature range of 490°C or higher and 1340°C or lower. In addition, position sensors, three-dimensional sensors, displacement sensors, pressure sensors, weight sensors, acceleration sensors, vibration sensors, torque sensors, and The excellent properties of the alloy of the present invention can be further exhibited in various applied devices such as sensor complexes such as repel sensors, float switches, limit switches, and proximity switches.

[Brief explanation of drawings]

Figure 1 is a characteristic curve diagram showing the change in electrical resistance with respect to temperature for comparative alloys consisting of alloy numbers FP-18, FP-24, FP-8 and palladium-43% silver in processed and annealed states. The figure shows alloy number FP-18 (palladium-13.5% iron alloy)
A characteristic curve diagram comparing the change in electrical resistance with respect to the number of days of thermal aging at a constant temperature of 1000℃ for 50 days or less in air, vacuum, or non-oxidizing gas. Figure 3 is for palladium-iron alloy. , Temperature Range (800~900℃), Temperature Range (900~1000℃) and Temperature Range (800~1000℃)
temperature coefficient of the average electrical resistance C _f (),
C _f () and C _f () and characteristic curve diagrams showing changes in specific electrical resistance ρ ₉₀₀ at 900°C with respect to palladium content. Figure 4 shows palladium 59.0 to 88.0% and iron
For the alloy of the present invention consisting of 41.0 to 12.0%, the temperature coefficient of electrical resistance C _f is ±100 ppm/℃ or less and ±
It is a characteristic diagram showing a temperature range having 50 ppm/°C or less.

Claims (1)

[Scope of Claims] 1 Consisting of 72.0 to 86.5% palladium and the balance iron and a small amount of impurities by weight, and has a temperature coefficient of electrical resistance of ±50 ppm/°C in the temperature range from the ordered-irregular transformation temperature to the melting point. An alloy having a small change in electrical resistance over a wide range of temperatures, characterized by having the following: 2 An alloy consisting of 72.0 to 86.5% palladium by weight, the balance iron, and a small amount of impurities is melted, cast, and heated in a vacuum or non-oxidizing atmosphere to a temperature above the ordered-disorder transformation temperature and below the melting point. hold in
After rapidly cooling from this temperature to room temperature, it is cold-worked into a desired shape such as a wire or plate, and this material is further heated at a temperature above the regular-disorder transformation temperature and below the melting point in a non-oxidizing atmosphere or in a vacuum.
After holding for at least 50 hours, cool at a cooling rate of 5 to 300°C/h until the regular-irregular transformation temperature (approximately 570°C)
In the temperature range above and below the melting point, the temperature coefficient is ±
A method for producing an alloy with a small change in electrical resistance over a wide range of temperatures, characterized by obtaining an alloy with a resistance of 50 ppm/°C or less.